Fig. 1. Photoisomerization of the EAZO moieties induced by CL. (a) Normalized absorption spectra of CPT and CPPO in a 1 : 9 DMF–PBS solution, PEAZO-PCD NPs and CLDRSs in PBS. (b) CL intensities of CPT (5 μg mL^–1, 1 mL), CPPO (5 μg mL^–1, 1 mL) and PCD (10 μg mL^–1, 1 mL) as a function of H₂O₂ concentration in a 1 : 9 DMF–PBS solution. The inset is a photograph of the before (1) and after (2) generated CL in the dark, taken at 10 s after addition of H₂O₂ (0.05 M) with error bars and standard deviation (s.d.) (n = 3 replicates). (c) Normalized absorption of PEAZO-PCD NPs in PBS (pH = 7.4) and fluorescence (FL) and CL spectra of CPT in a 1 : 9 DMF–PBS solution. (d) The CL emission intensity of CPT which vanishes when the PEAZO-PCD NPs increases. (e) Schematic layout of the emission–reabsorption system. (f) Schematic layout of the change in the absorption spectra of EAZO moieties measurement system with a spectrophotometer containing the photomultiplier tube. Change in the absorption spectra of the PBS solution of PEAZO-PCD NPs (g) with and (h) without the CL irradiation for different times. (i) Multiple rounds of cis–trans isomerization of EAZO with alternating CL of CPT and external yellow light (>570 nm) irradiation in PBS solution.